Titanium in metallic form or as a compound is an important element in the chemical series. For example, titanium dioxide is utilized in paint pigments, in white rubbers and plastics, floor coverings, glassware and ceramics, painting inks, as an opacifying agent in papers, etc. The other titanium compounds are used in electronics, as fire retardants, waterproofing agents, etc. The metal may be used as such or in alloy form as structural material in aircraft, in jet engines, marine equipment, textile machinery, surgical instruments, orthopedic appliances, sporting equipment, food handling equipment, etc. Heretofore in recovering the titanium from titanium bearing sources such as ilmenite, rutile, etc., the titanium has been subjected to separation steps which involve the formation of titanium as a compound in a valence state of +4, such compounds usually involving titanium oxide. However, when attempting to separate titanium dioxide from impurities which are also contained in the ore such as iron, the hydrolysis of the titanium dioxide at elevated temperatures usually results in also obtaining relatively large amounts of iron along with the titanium.
In contradistinction to the previous method of obtaining titanium from a titanium bearing source, it will hereinafter be shown in greater detail that it is possible to selectively crystallize iron and titanium in separate steps whereby a more efficient separation of the two metals can be accomplished thereby rendering the obtention of relatively pure titanium in a more economical manner.
This invention relates to a novel method for obtaining titanium metal values from a titanium bearing source. More specifically, the invention is concerned with a process for recovering titanium from a titanium bearing source such as ilmenite whereby a sharper separation of titanium from impurities contained therein may be accomplished.
It is therefore an object of this invention to provide an improved process for the production of titanium.
A further object of this invention is to provide a hydrometallurgical process for the production of titanium from titanium bearing sources.
In one aspect an embodiment of this invention resides in a process for obtaining titanium metal values from a titanium bearing source which comprises the steps of: (a) subjecting said titanium bearing source to a reductive roast; (b) leaching the resultant roasted source with aqueous hydrogen chloride at an elevated temperature; (c) cooling and saturating the leached solution with gaseous hydrogen chloride to precipitate ferrous chloride; (d) separating the precipitated ferrous chloride from the soluble titanium compound; (e) raising the temperature of the solution of the titanium compound to precipitate said titanium compound; and (f) separating and recovering the crystallized titanium compound from the leach liquor.
A specific embodiment of this invention is found in a process for obtaining titanium metal values from a titanium bearing source which comprises subjecting said titanium bearing source to a reductive roast at a temperature in the range of from about 600.degree. to about 900.degree. C., leaching the resultant roasted source with aqueous hydrogen chloride at a temperature in the range of from about 80.degree. to about 110.degree. C., cooling and saturating the leached solution with gaseous hydrogen chloride at a temperature in the range of from about 0.degree. to about 20.degree. C. to precipitate ferrous chloride, separating the precipitated ferrous chloride from the soluble titanium compound, heating the solution of the soluble titanium compound to a temperature ranging from about 20.degree. to about 30.degree. C. to precipitate the titanium compound in the form of titanium trichloride, separating and recovering the resultant crystallized titanium trichloride from the leach liquor.
Other objects and embodiments will be found in the following further detailed description of the present invention.
As hereinbefore set forth the present invention is concerned with an improved process for obtaining titanium metal values from a titanium bearing source such as ores including ilmenite, rutile, etc. The improvement comprises treating the titanium in a +3 valence state rather than a +4 valence state. The process is effected by subjecting a titanium bearing source which also contains other metals, principally iron, to a reductive roast at an elevated temperature which will range from about 600.degree. to about 900.degree. C. or more in the presence of a reducing gas such as hydrogen or carbon monoxide. In the preferred embodiment, the reductive roast is effected on a metal bearing source such as an ore, which has been crushed to a particle size less than about 100 mesh, at a temperature of about 750.degree. C. for a period ranging from about 0.5 up to about 2 hours or more. The reducing atmosphere which is used to accomplish the purpose of the roast usually comprises a mixture of about 50% carbon monoxide and 50% hydrogen with an excess of reductant being utilized in order to completely reduce the iron which is present in the system to the metal. Following the reductive roast of the metal bearing source, the source is then subjected to an aqueous hydrogen chloride leach which is also effected at an elevated temperature usually in the range of from about 80.degree. to about 110.degree. C. for a period of time ranging from about 0.25 hours up to about 1 hour or more in duration. Upon completion of the leach step, the resulting solution is thereafter cooled to a temperature ranging from about 0.degree. to about 20.degree. C. in order to effect a crystallization or precipitation of the ferrous chloride. The cooled solution, which is maintained in the subambient range hereinbefore set forth by external means such as an ice bath, cooling coils, etc., is then saturated with gaseous hydrogen chloride in order to insure a complete precipitation of the iron. After subjecting the solution which contains solid ferrous chloride and soluble titanium chloride to the aforesaid saturation step for a period of time which may range from about 0.5 up to about 2 hours or more in duration, the solution is subjected to a solid/liquid separation whereby the solid ferrous chloride crystals are separated from the soluble titanium compound contained in the leach liquor.
The solid ferrous chloride crystals may then be washed with water and treated at an elevated temperature of about 250.degree. C. whereby gaseous hydrogen chloride is removed and recycled to the saturation and precipitation step of the process, the solids which comprise ferric oxide and gangue being removed and recovered.
The pregnant leach liquor which contains the soluble titanium chloride compound is then passed to a warming stage wherein the temperature is raised to a range of from about 20.degree. to about 30.degree. C. In this warming stage the soluble titanium chloride will precipitate out as hydrated titanium trichloride crystals. Thereafter the desired titanium trichloride may be separated from the leach liquor by any means known in the art such as decantation, filtration, etc., and passed to storage as such or converted to titanium dioxide or titanium metal.